Embodiments of the subject matter disclosed herein generally relate to methods and systems and, more particularly, to mechanisms and techniques for sealing an actuator rod in a variable inlet vanes system.
During the past years, the importance of compressors in various industries has increased. The compressors are used in engines, turbines, power generation, cryogenic applications, oil and gas processing, etc. Therefore, various mechanisms and techniques related to compressors are often subject to research for improving the efficiency of this turbomachine and solving problems related to specific situations.
Actuation systems are used in various equipments, such as, compressors, pumps and expanders, to apply a force in order to modify a current state of the equipment. For example, an actuation system may operate adjustable inlet guide vanes (IVG) used in compressor applications to adjust an angle of incidence of inlet air into a compressor rotor and to control an amount of inlet air such as to ensure proper surge and to maximize efficiency.
An example of an adjustable IGV system 100 is shown in FIG. 1, which is reproduced from M. Hensges, Simulation and Optimization of an Adjustable Inlet Guide Vane for Industrial Turbo Compressors from the Proceedings of ASME Turbo Expo 2008: Power for Land, Sea and Air (Jun. 9-13, 2008), the entirety of which is hereby incorporated by reference. The adjustable IGV system 100 includes an actuator lever 102 directly connected to a first vane 104. The first vane 104 is connected via a drive arm 106 to a driving ring 108. The first vane 104 is rotatably attached to a guide vane carrier 110. A plurality of other vanes 112 are rotatably attached to the guide vane carrier 110. The plurality of vanes 112 are actuated by a plurality of linkages 114 that are connected to the driving ring 108. Thus, when the actuator lever 102 is rotated, it determines a rotation of the first vane 104 but also a displacement of the driving ring 108, which results in a movement of the plurality of linkages 114 and a rotation of the plurality of vanes 112.
FIG. 2 illustrates a manner of operating the adjustable IGV system (here 116 is a guide vane carrier). At a contact point 118, an actuation force F applied from an actuation bar 120 is transferred to the driving ring 108. The actuation force transmitted via the actuator rod 120 is generated by an actuation device 130. The actuation device 130 is controlled and/or monitored at least in part by control electronics 140 that is located inside the actuation device.
Given the potentially damaging environment in which the adjustable IGV system 100 may operate (for example, when used in a natural gas installation), the control electronics 140 is isolated from this environment. Conventionally, this separation of the control electronics 140 from the environment is achieved using mechanical seals, for example, a dynamic seal energized by springs closing a space between the body of the actuation device 130 and the actuator rod 120.
It has been observed that the mechanical seals do not operate satisfactory. Moreover, sometimes the gas in the environment (i.e., outside the actuation device) has low (cryogenic) temperature and, therefore, the chilled actuator rod 120, which extends inside the body of the actuator device 130 and is a good heat conductor, may determine ice formation (by condensation of the humidity inside the case). The ice may block the actuators bar's movement.
Further, if the force is generated hydraulically, different pressures inside and outside the actuation device 130 may create further problems (e.g., imbalances and forces) and inefficiencies (e.g., a direction of the force may be altered), when the sealing is not effective.
Accordingly, it would be desirable to provide systems and methods that avoid the afore-described problems and drawbacks.